Isn't there an on-by-default option that causes Windows to behave differently wrt. updates if you're on a metered connection? Still, it's on the user to mark their connection as metered...

The "this is a metered connection" toggle will only appear for wireless devices. There is no way to enable it when on a wired network.

Source: Much googling after I found myself on a hotel's low-bandwidth network for a week.